'01 24v Cummins, auto, 3.54 gear, 35" tall tires, 4x4, quad cab short bed.
4" straight pipe exhaust, BHAF, and a small 60 hp Superchips programmer.

Mine gets around 20-21 mpg combined city/highway (mostly highway). Don't do much city driving w/ it and I've honestly never even bothered to check the mileage when towing. I check it by hand, although the dash/overhead readout is always real close as far as the average mpg.